Gasolines comprising petroleum hydrocarbons have been used for a long time as fuels for Otto cycle type internal combustion engines. However, the oil crises that occurred repeatedly in 1973 and 1979 led to investigations of various fuels to be used as petroleum substitutes. Of these, methanol is expected to be the most promising substitute fuel for use in Otto cycle type internal combustion engines. In the United States, methanol is also regarded as a promising measure against photochemical smog which is a serious cause of urban environmental pollution. For these reasons, experiments on methanol fuels are being made in various countries in the world including the United States and Japan.
However, methanol has the following drawbacks as indicated, for example, in Proceedings of VIII International Symposium on Alcohol Fuels, (Nov. 13-16, 1988, Tokyo), pp. 851-868:
(a) at low temperatures, methanol has poor engine-starting performance and may be unable to start the engine;
(b) if methanol catches fire in an accident, the flame is invisible and this is dangerous; and
(c) in an enclosed state such as in a fuel tank, ordinary temperatures are within the combustion range for the gaseous phase and, hence there is the danger of fire or explosion.
As an expedient for overcoming these drawbacks, blending of methanol with around 15% by volume of a gasoline or the like is generally done. In this case, automotive gasolines on the general market, catalytically reformed gasolines, straight-run light naphthas, isopentane, and so forth are employed as the blending gasoline or the like.
Although blends of methanol with these gasolines or the like have the aforementioned inflammation-avoiding effect (c), blending components respectively have the following problems:
(1) automotive gasolines produce a low temperature starting-improving effect (a) and flame visibility-improving effect (b) (referring to the aforementioned drawbacks), but these effects are still insufficient. Further, there are cases where these improving effects are varied by a difference in production method or the lot of the gasolines;
(2) catalytically reformed gasolines are good in (b) but are still insufficient in (a);
(3) straight-run light naphthas are good in (a) but are still insufficient in (b); and
(4) isopentane is good in (a) but is insufficient in (b). Further, it is expensive and is uneconomical.